A prior art elongated lighting system can be constructed with a light pipe and first and second light sources at the first and second ends of the light pipe, respectively. The light pipe is provided with light-extraction means along some portion of the length of the light pipe, to extract light from the side of the light pipe. In a typical configuration, the light travels in light rays along the length of the light pipe and some of these light rays strike light-extraction means and are extracted from the side of the light pipe, and can be used for illumination or other purposes. However, some amount of light rays introduced into the light pipe by the first and second light sources do not strike the light-extraction means. This is because those light rays either propagate straight through the light pipe or only make a limited number of total internal reflections, or bounces, within the light pipe and do not strike the light-extraction means. The light rays that are not extracted by the light-extraction means are wasted, such as by encountering points in the light pipe, such as impurities, where light absorption occurs, or the light rays may reach either of the light sources and be absorbed. Such light rays, that do not reach the light-extraction means, undesirably represent a loss in efficiency of the lighting system.
It would be desirable to provide an elongated lighting system having light-extraction means along a length of a light pipe, provided with light at first and second ends, which is able to capture and extract a significant amount of light that would otherwise not reach, and be extracted by, the light-extraction means. This would increase the efficiency of an elongated lighting system of the foregoing type.